Submarine cables having anti kink armouring



July 7, 1959 A. 1.. MEYERS SUBMARINE CABLES HAVING ANTI KINK ARMOURINGFiled Oct. 10, 1955 United States Patent i SUBMARINE CABLES HAVING ANTIKINK ARMOURING Arthur Lennox Meyers, Herne Hill, London, England,

assignor to Submarine Cables, Limited, London, England, a company ofGreat Britain Application October 10, 1955, Serial No. 539,561

Claims priority, application Great Britain October 15, 1954 5 Claims.(Cl. 174-408) This invention relates to submarine cables and isconcerned with an improved construction of armouring for use therewith.

It has long been recognised that in a deep-sea submarine cable having asingle layer of armouring wires there is a tendency to producedeletereous effects due to the twisting of the cable, and particularlyis this so in a cable having repeater apparatus or the like at spacedintervals, since at those sections of the cable on each side of therepeater apparatus it will be found that the turns in the cable tend topile up under longitudinal tension, which 1 occurs during the operationsof laying and recovery by the cable ship, with the result that kinks maybe formed in the cable which may cause electrical faults or evencomplete breakage.

Trouble is liable to occur particularly when picking up cable connectedto a repeater during repair or recovery operations. At this time thearmour wires will be subjected to a heavy load due to the weight of thesuspended cable and perhaps also of an attached repeater, andconsequently axial twisting occurs. Provided the longitudinal tensionwere steady, this twisting of itself might not have any seriousconsequence; but in practice it is not steady. For example, the rise andfall of the ship in an ocean swell causes variation of the tension, andwaves of augmented and diminished tension travel down the cable, withconsequent variations in the degree and rate of axial twist. Therepeater, owing to friction against the seabed, or, when suspended toits bulk and mass, partially interrupts the waves of axial twist. Theresult is that under momentarily relaxed tension near the bottom, thereis a tendency for the cable to be thrown into turns or coils, and forthe turns to accumulate at or near the repeater. Under continuedtension, as the ship rises or the cable continues to be picked up, theseturns may be drawn out into kinks, which may cause electrical faults.Breakage of the cable under the full tension as the kinks approach thesurface may make it impossible to recover the repeater.

In order to overcome this difiiculty it has been proposed to provide adouble layer of armouring wires, the wires of the outer layer beinghelically applied in the opposite direction to the wires of the innerlayer, the purpose being to ensure that the tendency of one layer tocause twisting is balanced by that of the other layer to cause twistingin the opposite direction.

It will be appreciated moreover, that the provision of two layers ofarmouring wires for the whole length considerably increases the cost ofproduction of the cable quite apart from the appreciable increase inweight, which is undesirable.

It might be considered that an appreciable length of double armouredcable could be used in the vicinity of the repeaters spliced to a singlearmoured cable which comprises the majority of the length of the cablebetween repeaters. The objection to such an arrangement is that thesudden change in the torsional properties of the cable at the junctionbetween the two types again partially in- 'ice terrupts the waves ofaxial twist, and that there is then a tendency for turns to be thrownand for kinks to be formed at or near the junction.

According to the present invention in a submarine cable having anarmouring and provided with repeater apparatus or other insertions thearmouring comprises sections extending between each repeater apparatusor insertion in which the armouring structure remains torsionallyunbalanced for the greater portion of the section but is such that inthe vicinity of the repeater or insertion it is substantially balanced,the balanced and unbalanced sections being joined to one another by anintermediate armouring structure such that the change over from thebalanced to the unbalanced portions is a progressive one, therebypreventing any appreciable change in torsional properties at any oneplace.

In practice it will result in the Waves of axial twist beingprogressively reduced in amplitude without serious partial interruptionat any one place, so that the tendency to throw turns and form kinks iseliminated. Moreover this benefit is obtained without undue increase inthe overall cost of the cable.

The desired graduation of the torsional properties of the cable can beobtained by continuing the armour Wires of the single armoured cablewithout alteration up to the repeater and by applying over them a secondlayer of armour wires in the opposite direction, the angle of lay of thewires with respect to the axis and/ or the diameter of the wires and/ orthe number of wires in the second and outer layer being progressivelyincreased until substantial torsional balance is obtained in the doublearmoured cable next to the repeater. Alternatively, the desiredgraduation can be obtained by progressively altering the angles of layand/or the numbers and/or the diameters of wires in both the inner andouter layers.

The distance over which the progressive graduation in the torsionalproperties of the cable is eliected may be as short as fathoms, or mayextend to 1000 fathoms or more. It is desirable to have a considerablelength, say 100 fathoms or more of substantially balanced doublearmoured cable next to the repeater.

The invention is illustrated in the accompanying drawing in which Fig. lis a diagrammatic view of a submarine cable provided at intervals withrepeater apparatus,

Fig. 2 is a side elevation, on a non-uniform longitudinal scale, asection of cable having progressively graduated torsional properties,

Fig. 3 is a transverse section through the substantially torsionallybalanced cable next to a repeater and approximately on the line III-IIIof Fig. 1.

In Fig. l of the drawings S indicates a length of cable joining tworepeater apparatus indicated generally at R R which it will beunderstood occur at regular intervals throughout the submerged length ofthe cable.

Referring now to Figs. 2 and 3 of the drawings there is shown asubmarine cable wherein the cable conductors form a coaxial structure,comprising an inner copper conductor C, insulated by a layer A ofthermoplastic insulation material, such as polyethylene, outside whichis an outer conductor B consisting of a layer of copper tapes appliedhelically and held in position by a copper binding tape D. As shown insection in Fig. 3, the cable core is surrounded, in accordance withstandard practice, by an inner serving 15 of jute yarn over which is theinner layer of armour wires 16, consisting in this case of 21 galvanisedsteel wires each of 0.095" diameter, applied helically with a left handlay of 16''. This layer of armour is continued unchanged from therepeater R which is to the left of Fig. 1, through the special sectionshown in Fig. 1, to form the single armour of the majority of the cablelength, to the right of Fig. l, and up to the next repeater, R andthrough the entire length of the cable between repeaters.

Referring again to Fig. 3, the layer of armour wires 16 is surrounded byanother serving 17 of jute yarn secured by a whipping of jute (notshown). Over the jute serving layer 17 is the outer layer of armourwires 18 which extends up to the repeater R and constitutes with theinner layer 16 of armour wires the double armouring. The outer layer inthis case consists of 34 galvanised steel wires each of 0.072 diameter,applied helically with a right hand lay of 26". Finally this outer layer18 of armour is covered by an outer serving 19 consisting of two layersof jute yarn applied in opposite directions. As shown in Fig. 3, eacharmour wire may be protected from corrosion by an individual covering oftar compound held in position by a fabric tape, or by an individualcoating of extruded plastic material such as polyvinylchloride. As afurther protection the cable is completed with a coating of tar compoundoverall.

The number, dimensions and lays of the armour wires are such that thefully double armoured cable next to a repeater is substantiallytorsionally balanced, so that it does not twist axially when subjectedto longitudinal tension.

The novel feature of the invention is illustrated diagrammatically inFig. 2, which shows how the torsional properties of the cable may beprogressively graduated in steps or stages from the non-twisting fullydouble armoured cable to the left of Fig. 1 to the twisting singlearmoured cable to the right of Fig. 2. Thus section 1, which may have alength of 100 fathoms or more, shows the fully double armoured cablenext to a repeater. At the beginning of section 2, which represents asubstantial length of cable for example 25 fathoms in Example No. II or80 fathoms in Example No. III, certain of the wires, as indicated at 2Ain the outer layer of armour are cut and thus terminated i.e. they areomitted from, the outer layer. This process is continued in sections 3,4 and 5, where the terminated wires are indicated respectively at 4A and5A both of which represent substantial lengths of cable, and in furthersections not shown in the drawing, until in section 9 only a few wiresremain in the outer layer. These few wires are omitted at the beginningof section 10, so that the cable then contains only a single layer ofanmour wires. The gaps left by the removal of wires are filled with juteyarn as indicated 2B in section 2 and 3B in section 3. The cut ends aresecured by bindings 20. The outer serving 19 is carried over the specialsection of cable, and is tapered down at the single armoured end, whereit may be bound down or continued to form the outer serving of thesingle armoured cable.

In accordance with the invention, a special section of cable such asillustrated and just described, is provided on each side of eachrepeater to be laid in deep water.

Example I A short length of cable, made up for test purposes and all ofwhich was armoured with 16/ 13 E.W.T. wires, had applied to it at oneend, a second and outer layer of armouring with the wires arranged inopposite lay, the wires in the outer layer being reduced at intervals soas to give the following reductions:

28/15 wires for 15 yds. reduced to 21/15 wires for ten yds., reduced to14/15 wires for ten yds., finally reduced to 7/15 wires for ten yds.

Tests on this short length of cable demonstrated that the progressivegraduation in the number of Wires in the outer armour prevented anysudden change in the torsional properties of the cable.

Examples II and III set out below show examples of designs, inaccordance with the invention, of tapered double armoured cable intendedfor use at sea. In both these cases the inner layer of armour consistsof 21 steel wires each of 0.095" diameter, with a left hand lay of 16",continued unchanged to form the single armour of the majority of thecable between repeaters; and the outer layer of armour, at the fullydouble armoured end next to a repeater, consists of 34 steel wires eachof 0.072" diameter applied with a right hand lay of 26". The angle oflay of the outer layer is not changed, but the number of wires in theouter layer is progressively reduced in 7 steps in Example II and in 11steps in Ex ample III.

Example 11 Length fathoms Number Then remove wire numbers of wiresExample III Length fathoms Number Then remove wire of wires numbers iThe wires are removed in as symmetrical a manner as is convenientlypracticable, as shown in the above examples. The ends of the cut wiresare bound down securely, and the spaces resulting from the removal ofthe wires are filled with jute. A normal outer serving of jute iscarried over the complete taper, and the cable is finished with a normalcoating of tar compound.

Although in the examples given above the torsional graduation isobtained in steps by altering the number of wires in the outer layer, itis clear, as has already been stated that, in accordance with theinvention, the desired graduation may be obtained by altering, insteador in addition, the angle of lay and/or the diameter of the wires. Itmight be thought that the best result would be obtained by a continuousalteration of the angle of lay, as this would give a continuousgraduation instead of a graduation in steps; however, not only is thisdifficult to carry out in practice, but also such refinement has notbeen found necessary.

Although the invention has been described and illustrated in relation toa cable in which the tensile elements are wires, it is clear that thedesired torsional graduation may similarly be obtained with tensileelements of shapes other than circular.

It will be understood that the invention is also applicable to otherinsertions, such as loading coils, which may cause similar mechanicaldiflicuities.

What is claimed is:

l. A submarine cable comprising a conductor, an insulation for theconductor and an armouring surronnding the insulated conductor, and inwhich electrical repeater apparatus are provided at intervals in thecable length, in which the armouring comprises a stranded inner layer ofwires applied continuously over those sections of the cable between therepeater apparatus and adjacent to the ends of each of such repeaterapparatus, an outer stranded layer of wires, the wi res in the outerlayer being of opposite lay to the wires of the inner layer andextending from the respective repeater apparatus towards the nextrepeater apparatus to ,provice a double armoured cable portion adjacentto the repeater apparatus, but

terminating short of the next adjacent repeater apparatus to leave anintervening single layer armoured cable section, the number of wires inone of said layers decreasing in stages each at least ten yards longfrom the repeater apparatus to the adjoining single layer armouredportions of the cable, whereby the tendency of the cable to twistincreases progressively in stages from a substantially zero tendency totwist in the fully double armoured portions adjacent to the repeaterapparatus to the single armoured portions of said cable.

2. A submarine cable as claimed in claim 1 in which the inner layer ofarmour wires in the double armoured portions of the cable continuesunchanged throughout the length extending between repeater apparatus toprovide the armour in the single armoured portion and in which thenumber of wires in the outer layer at the start of each stage isreduced.

3. An armoured submarine cable in accordance with claim 1 in which thenumber of wires in both layers at the start of each stage is reduced.

References Cited in the file of this patent UNITED STATES PATENTS1,873,798 Varney Aug. 23, 1932 2,041,269 Smith et a1. May 19, 19362,414,045 Kitselman Jan. 7, 1947 2,754,351 Horn July 10, 1956 OTHERREFERENCES Transactions of The A.S.E.E., vol. 70, Part 1, pages 565-566,1951, copy in Division 69, 174-701

